Reproductive ecology of five sympatric Agave Littaea (Agavaceae) species in central Mexico

摘要

We studied a community of Agave species that coexist in the Metztitlán Canyon in Central Mexico. During 2001, 2002, and 2003, we analyzed floral traits and rosette allometry in five species belonging to the subgenus Littaea: A. celsii albicans, A. xylonacantha, A. difformis, A. striata, and Agave sp.; and observed floral visitors for each species. We report the first evidence of bat visitation in the subgenus Littaea and find that bats (Leptonycteris curasoae, Choeronycteris mexicana, and Glossophaga sp.) are the primary pollinators in four species. Honeybees, hummingbirds, bumblebees and hawkmoths were also common visitors. We propose that the presence of diurnal pollinators may increase the reproductive success of the plant when offering pollinator services additional to the coadapted pollinator. We also found evidence of selection pressures toward semelparity because pollinators are selecting for taller inflorescences in three of the five species. There is phenological complementarity in this community because the flowering periods of the five species span the entire year, although there are some periods when pairs of species overlap. Additionally, we found evidence for character displacement in rosette sizes and separation of spatial and temporal resource use in pollinator composition among species.